A Finite Radiative Self-Energy and Propagator Doorway for an Electron-Like Packet in the ECSM Framework

This paper presents the V26 stage of the ECSM electron-like packet programme. The construction inherits the V21b–V25 chain: near-electron rest-energy packet recovery, coherent-limit Dirac-like propagation, emergent gauge coupling, Pauli-limit tree-level magnetic coupling with g = 2, and a Schwinger-scale one-loop magnetic-moment doorway. V26 tests the next structural layer: whether the inherited ECSM electron-like packet admits a finite radiative self-energy and propagator doorway without fitted mass repair or uncontrolled cutoff divergence. The notebook reconstructs the inherited Dirac/Pauli algebra, verifies the free propagator pole structure, audits a finite-difference gauge-response vertex identity, introduces a finite-response self-energy kernel, and compares its cutoff behaviour against an unsaturated raw reference. The raw reference remains cutoff-sensitive, while the ECSM response-regulated kernel saturates. The final audit passes 13/13 criteria and is labelled PASS_STRONG_DOORWAY. This work does not claim full QED, complete renormalisation, Lamb shift, scattering amplitudes, vacuum polarisation, running coupling, or a measured physical electron self-energy prediction. It establishes a finite radiative self-energy and propagator doorway for the inherited ECSM electron-like packet.